SV-POW! showdown: Supersaurus vs Brachiosaurus and Diplodocus

July 13, 2014

Now think of this. Its neck is 8.5m long. Knock of one measly meter — for example, by removing one vertebra from the middle of the neck — and you have 7.5 m.

Supersaurus’s neck was probably TWICE that long.

Holy poo.

I replied that I was indeed freaked out, and that it had given me an idea for a post, which you are now reading. I didn’t have a Giraffatitan that was sufficiently distortion-free, so I used my old trusty Brachiosaurus. The vertebra you see there next to Mike and next to the neck of Brachiosaurus is BYU 9024, the longest vertebra that has ever been found from anything, ever.

Regarding the neck length of Supersaurus, and how BYU 9024 came to be referred to Supersaurus, here’s the relevant chunk of my dissertation (Wedel 2007: pp. 208-209):

Supersaurus is without question the longest-necked animal with preserved cervical material. Jim Jensen recovered a single cervical vertebra of Supersaurus from Dry Mesa Quarry in western Colorado. The vertebra, BYU 9024, was originally referred to “Ultrasauros”. Later, both the cervical and the holotype dorsal of “Ultrasauros” were shown to belong to a diplodocid, and they were separately referred to Supersaurus by Jensen (1987) and Curtice et al. (1996), respectively.

BYU 9024 has a centrum length of 1378 mm, and a functional length of 1203 mm (Figure 4-3). At 1400 mm, the longest vertebra of Sauroposeidon is marginally longer in total length [see this post for a visual comparison]. However, that length includes the prezygapophyses, which overhang the condyle, and which are missing from BYU 9024. The centrum length of the largest Sauroposeidon vertebra is about 1250 mm, and the functional length is 1190 mm. BYU 9024 therefore has the largest centrum length and functional length of any vertebra that has ever been discovered for any animal. Furthermore, the Supersaurus vertebra is much larger than the Sauroposeidon vertebrae in diameter, and it is a much more massive element overall.

Neck length estimates for Supersaurus vary depending on the taxon chosen for comparison and the serial position assumed for BYU 9024. The vertebra shares many similarities with Barosaurus that are not found in other diplodocines, including a proportionally long centrum, dual posterior centrodiapophyseal laminae, a low neural spine, and ventrolateral flanges that connect to the parapophyses (and thus might be considered posterior centroparapophyseal laminae, similar to those of Sauroposeidon). The neural spine of BYU 9024 is very low and only very slightly bifurcated at its apex. In these characters, it is most similar to C9 of Barosaurus. However, theproportions of the centrum of BYU 9024 are more similar to those of C14 of Barosaurus, which is the longest vertebra of the neck in AMNH 6341. BYU 9024 is 1.6 times as long as C14 of AMNH 6341 and 1.9 times as long as C9. If it was built like that of Barosaurus, the neck of Supersaurus was at least 13.7 meters (44.8 feet) long, and may have been as long as 16.2 meters (53.2 feet).

Based on new material from Wyoming, Lovelace et al. (2005 [published as Lovelace et al. 2008]) noted potential synapomorphies shared by Supersaurus and Apatosaurus. BYU 9024 does not closely resemble any of the cervical vertebrae of Apatosaurus. Instead of trying to assign its serial position based on morphology, I conservatively assume that it is the longest vertebra in the series if it is from an Apatosaurus-like neck. At 2.7 times longer than C11 of CM 3018, BYU 9024 implies an Apatosaurus-like neck about 13.3 meters
(43.6 feet) long.

Bonus comparo: BYU 9024 vs USNM 10865, the mounted Diplodocus longus at the Smithsonian, modified from Gilmore 1932 (plate 6). For this I scaled BYU 9024 against the 1.6-meter femur of this specimen.

If you’d like to gaze upon BYU 9024 without distraction, or put it into a composite of your own, here you go:

References

Gilmore, C. W. 1932. On a newly mounted skeleton of Diplodocus in the United States National Museum. Proceedings of the United States National Museum 81, 1-21.

This is probably a really, really stupid question, and I fully expect to be schooled on this, but is there a possibility that Amphicoelias Fragillimus was just a *really* big Supersaurus, akin to how “Seismosaurus” is a really big Diplodocus?

Or are there exitant caudial verts from Supersaurus that indicate there’s a huge difference between the two?

We know from the drawing that the vert had a lot of odd little laminae, and we know from the written description that the bone was very thin and fragile–hence the name–which implies a high ASP. Both of those are expected in a big diplodocid. One weird thing about the big Oklahoma Apatosaurus is that the dorsal vertebrae have more complex pneumatic fossae than other specimens of Apatosaurus–you can see a bit of this in Text-Fig. 3 of my prosauropod paper. So maybe the vertebrae of giant individuals of known taxa tend to be more pneumatically complex, because that’s part of how they got so big in the first place. If that’s true, the pneumatic complexity of A. fragillimus is size-related, and not necessarily taxonomically informative. Given how much diplodocid dorsals vary serially, I think A. fragillimus could be a giant individual of just about anything. Supersaurus is especially hard to rule out, since we don’t have a complete dorsal series.

Fantastic! Admittedly, I’m more of an armchair amateur at this sort of thing, (okay, pretty much entirely armchair) so I wasn’t sure if I was thinking properly on this or not.

Sidenote, has anyone compared the pneumacitity of D. hallorum to the other species of Diplodocus on some quantifiable level? (Could anything like that be even possible? ) It might be a good benchmark for such comparisons of giant individuals, or at least, a start…. or between the giant Oklahoma specimen of Apatosaurus to other, more average specimens?

Nothing on D. hallorum as far as I know, although it’s possible that someone is on it. I’d be interested to find out how far down the tail pneumatic fossae are present in D. hallorum–in other specimens of Diplodocus, the last pneumatized caudal is usually between caudal 16 and caudal 19. Would certainly be interesting if D. hallorum had a different pattern.

If old Amp really was a trophy Supersaurs it would have been mind-bogglingly large. If Supe’s 10th dorsal was ~1.3m tall, and A. fragillimus was ~2.4-2.7m we are looking’ at a 60-70 meter beast! Bonus: It would also get a much more awesome name.

On a related note, does anyone know exactly how tall Supersaurus’s dorsals are??

I don’t see what Supersaurus has to do with this–if you estimate the A. fragillimus dorsal at 2.7 meters you end up with a prodigious animal no matter what reference taxon you scale up from. But remember that Mike got a 2.3 meter vert, a 49-meter body length, and a body mass of roughly 80 tons in this post, which seems just as fair on methodological grounds as the bigger estimates.

Just that even using the 2.3 meter vert will give you a speculative animal measuring 56 meters long, and weighing roughly 150 tons. Even with Supersaurus’s shortish tail. That is, assuming Supe’s 10th dorsal really is 130cm tall. Is there any hard data out there on the dimensions? I tried eyeballing it when I was at the Wyoming Dinosaur Center, but they were too far away! ;)

Well, Matt’s writing about the BYU Supersaurus — the one that was “described” by Jensen in 1985. This is the one that’s mostly been compared to Barosaurus (though mostly informally, and not by Jensen). What you saw at WDC is a different specimen known as “Jimbo”, which Lovelace et al. (2008) considered to be most closely related to Apatosaurus. Never having seen either of them for myself, I have basically no opinion on whether they’re the same thing, and if so then what other diplodocid they are best compared with. Frustratingly, the Lovelace et al. paper skims very briefly over their reasons for considering their new animal to be an individual of Supersaurus.

References

Jensen, James A. 1985. Three new sauropod dinosaurs from the Upper Jurassic of Colorado. Great Basin Naturalist45(4):697-709.

Lovelace, David M. Scott A. Hartman and William R. Wahl. 2008. Morphology of a specimen of Supersaurus (Dinosauria, Sauropoda) from the Morrison Formation of Wyoming, and a re-evaluation of diplodocid phylogeny. Arquivos do Museu Nacional, Rio de Janeiro65(4):527-544.

“Frustratingly, the Lovelace et al. paper skims very briefly over their reasons for considering their new animal to be an individual of Supersaurus.”

Those jerks! But you are right, upon review we spend too little time on the diagnosis. Sigh…

That said, nothing about the BYU specimen looks much like Barosaurus except the previously referred caudal series, which was in fact Barosaurus as best we could tell. I know that BYU 9024 has also been compared to barosaur cervicals, but there’s a reason it’s nicknamed “the spaceship”.

P.S. To be clear, it’s because of distortion and its resulting shape, not hyperdrive or ion cannons.

I’ve been reading up on the variability in herding strategies of differing sauropod taxa ,namely the mixed age vs age segregated herds discussion and evidence pointing to both occurences being plausible.

Just out of curiosity, since you”ve visited the Museum Naturkande in Berlin, any idea on the variability of age within the specimens of Giraffatitan housed within the institution ?